The present invention relates to valves, more particularly to diaphragm valves.
Diaphragm valves utilize a resilient diaphragm and a valve shoulder to engage a valve seat and prevent the flow of fluid past the valve seat. Diaphragm valves provide excellent sealing and isolation characteristics to contain fluid being controlled and prevent migration of the controlled fluid into the valve mechanisms or out of the valve.
In many applications, particularly in the semiconductor industry, the leakage of fluid must be strictly contained due to the corrosive nature of the controlled fluid. A diaphragm valve must be made of a material able to withstand such corrosive fluid while being capable of a large number of operations without repair or replacement. Actuators used to operate diaphragm valves are a potential location for leakage of fluid from the valve. The actuator must be sealed to prevent leakage and permit a mechanical force from outside the valve to operate the actuator.
In many applications in the semiconductor industry it is necessary to instantaneously change fluid flow to a particular process. Additionally, need arises to alternate a particular processes or equipment. This type of fluid switching can be accomplished with two two-way diaphragm valves and an external T-connection. However, when two two-way valves are used, the space requirement for mounting these valves and additional controls for separate control of each valve increases the cost of the installation.
The process fluids utilized in semiconductor processing applications may be highly costic and must be ultrapure. Contamination of these ultrapure fluids can cause catastrophic damage to wafers being processed into integrated circuits. A potential source of contamination is contact by the fluid with essentially any type of metal. Process control valves, particularly diaphragm valves, are generally capable of being manufactured of almost entirely all plastic, including fluoropolymer plastic materials. These plastic used do not contaminate the process fluids and are inert thereto. One portion of the plastic valves for which it is very difficult to replace is the metallic spring utilized to provide the normally opened and/or normally closed position of the valve. These springs are typically isolated from the fluid four courses by one of the valve members and associated diaphragms. However, failure of the single diaphragm separating the fluid flow courses from the metallic spring can cause contact with the metallic spring by the fluid and thereby cause contamination of the fluid. An additional safeguard to prevent such contamination is warranted.